I've got exactly 1/8 of an inch to go on each side before I can say I've made full use of my rear tire. And I think THAT would be plenty for me!
I do like the idea of a getting "down and dirty" with the smaller cc bikes. Call me crazy, but I would love to have a 250cc Kawi Ninja to flog the **** out of. Super light, small, agile, cheap (get one a few years old and you won't worry about messing it up), and relatively good performing. I would take it to track days and take it to the twisties to learn to ride better/faster. Maybe I'll even "drop a knee" someday.
The bike would certainly be able to go much faster than my capabilities so far. Just like the Big Foot and F1 analogy. What would be more fun to flog on a twisty road. Driving/riding a lesser machine 10/10ths on every day roads is much more fun than a full-on sporty/race machine that takes less skill.